Machine-switching telephone system



S. B. WILLIAMS, JR. MACHINE SWITCHING TELEPHONE SYSTEM.

' APPLICATION FILED NOV. 19, m9.

1,413,38; Patented Apr. 18, 1922.

lnvenfo Jamue/ B "l/l l'l/iamaJn 7 T all whom z'zimag concern. V Be it known that I, SAMUEL BJVVILL A 's, 1 Jr, a citizen of the United States, residing at Brooklyn, in the county of Kings and' SAMUEL B. WILLIAMS, .13., or BROOKLYN, NEW YORK, assrsn'on ro WES-TERN'ELEC 'rnic'co'ivrrenY; INCORPORATED, or newroan,1v. Y., econronarron or NEW ivmcnrnn-swrrcmns-rnnnrnonn srsrnlvrt State of New York, have invented certain new and useful Improvements in Machine- Switching Telephone Systems, of which thefollowing is a full,clear, concise, andexact description. 1

This invention relates to machine SWltCl-L ing telephone systems of the type in which talking current iszsuppliedgto the talking ment whereby a relay connected in series conductors throughimpedance coils, :and

supervisory relays in such systems.

vide, in,such a system, a circuityarranges with the' talking' conductors may be'made responsive to short interruptions of the" current ,in said conductors and may also-be used as a supervisory relay without. impair ng the transmission of voice current. 2 A feature. oflthe invention is the c'onnec-, tion'of a. capacity'element in parallel with .the source of talking current duringthe time that the seriesrelay is to beresp'onsive to impulses, and theremoval' oft-his; element when this relay :n'o longerv needs to' respond to.,--impulses.-- 4". n f- The 7 drawing shows the invention applied to a telephone systemusingtransmission or. the: repeating coil type, but it is obvious that it is equally applicable to systems us1ng any other type of transmission inwhlch talking current is supplied through impedance COllS.

Tothe left of the dotted line are shown diagrammatically the substation 1 of a call-I ing line, a line switch indicated bybrushes 3. 4, and 5 and a first selector swltchof the step-by-step type. Ontherlght of the dot- V ted line a connector switch and a called line are shown; Thesubstation of the-calling line is equipped with an impulse sender 2, which may be of any type which causes c1rcuit changes of short duration when ,op erated.

A subscriber at l'desiring to. initiate a call removes his receiver from its hook, thereby operating the line switch. to extendthe calling line through brushes 3, 4L and 5 to the terminals 6, 7 and 8 of an idle selector switch. A circuit isthereupon completed from grounded battery through the lower Specification o fiietter's' Patent! Pitliefillfitl 185 Application filed November 19,1919, SerialNo. 339,026. r v I left-hand winding of repeating coil 9, wind ing ofimpulse. relay 10, terminal 7, brush 4 through the call ng; line including the ap'-' paratus at station 1, brush 3, terminalo, upper lett-hand w nding-of repeating coil 9 to 1 ground." Belay v10 is energized in this air} cult and inattracting its armature energizes slow release relay 11; Relay 11, in attract ng lts inner armature, interposes a break in the circuit. of therelease magnet i andprepar'es a path'for'imp'ulses to oper-" ate stepping magnets. {In attracting its outerarniature, relay'll connects ground. to

terminal '8 tojholdv the line switch oper j busy. The V subscriber now operates his atedi and to render;themultiples of thei impulse. sender. 2 zto send the hundreds l Series of impulses; The sender2 in restoringfinterrupts the circuit'tracedifor impulse. r

relaynlO a'number of times corresponding withthe,hundredsdigitiof the called line. V [In response to the firstfinterruption ofit s circuit,relay lO retracts its armature com--"* pleting a circuitv from ground; armature and back contact ofrela'y 10, inner-armature and front. contact; of relay" 11, back contact and right handa'rmaturefof relay12,'through the I 1 winding of relay l3,sideiswitch arm 14 (po- I sition. Y1) throughth'e 'winding'of primary .magnet 15. [to grounded; battery. -Magnet 157B energized in this circuit and steps selector brushes'1 6, 1'7 and:18 one step in their primary direction. Slow release relay--13 is Y also energized in thiscircuit and being'slow to release will remain energized'throughout" each:ser1es ot impulses, In attracting its armature, relay 13 completes a circuit: from ground, front contact and armature of relay i3,.arms19 and 20 (position 1,), through the I I batteryw lvlagnet 21 is energized in thi'scir-,

winding of: escape magnet 21 tov grounded cuit but does not operatethe side switch until it is deenergized. f -lV'hen the selector switch is idle the'condenser 22 is-connected across the'talkingjconductors through arm 23 and is charged to the full potential of the battery. If condenser H 22 were notconn'ected across the line the relay 10 would deenergize upon the first interclose of this interruption, owing to the impedance vof the 'repeating coil and of the pedance of this path is relatively much lower than that of the circuit through the repeating coil 9, condenser 22 discharges-rapidly, thereby adding its discharge to the normal current, thus quickly building up the current through the winding of relay to a sufficient value to operate said relay. During the interruption of the line circuit, condenser 22 is recharged. Thus by the connection of a condenser in parallel with repeating coil 9, relay 1.0 is made responsive to short in 'l'erruptions of the line circuit, the effect of which would merely be to cause it to hold its armature retracted throughout such nnpulses if condenser 22 were not connected across the line.

Relay 1O vibrates its armature in response to the remaining impulses of the hundreds series, holding slow release relay 13 energized and ooera-tin ma net- 15 to S1363 i l a brushes 16,17and18 to the desired group of lines. At the conclusion of this series of impulses, relay 1O remainsenergized and after a short interval relay 13'retracts its armature to open the circuit of escape magnet 21 which thereupon is deenergized to move the side switch arms'to their second position. A circuit is immediately completed from grounded battery through the Winding of magnet 21. arm 2O (position 2), conductor 24, secondary ofi normal contact 25 to ground. Magnet in attracting its armature completes a circuit from grounded battery through the Winding of secondary magnet 26, armature and back contact of said magnet, front contact and armature of magnet 21, arm 27 (position 2), outer armature and front contact of relay 11 to ground. Secondary magnet 26 is energized in this circuit to step brushes 16, 17 and 18 into engagement with the first set of terminals in the selected group, thereby opening off-normal contact 25 and interrupting the circuit for escape magnet 21. If this set of terminals is busy, ground potential will be present on its test terminal 29 and will be e5:- tendcd through brush 18, conductor 24, arm 20 (position 2), through magnet '21, to grounded battery, to holdmagnet 21 energized. Secondary magnet 26 in attracting its armature makes and breaks its circuit, stepping brushes 1G, 17 and 18 over the group of terminals until an idle set-64, 28

and 29, distinguished by absence of ground. on test terminal 29, is reached. At this time there is no longer a circuit for magnet 21, which is deenergized, to pass the side switch arms to their third position. A circuit is now completed from ground, front contact and outer armature of relay 11, conductor 30,

in attracting its left-hand armature relay 33 interposes a break in the circuit of release magnet 31. y

The calling subscriber now operates his impulse sender to send a series of impulses corresponding to the tens digit of the called line. Relay 10, as before, vibrates its arma ture in response to these impulses, at each retraction of its armature completing a circuit from ground, armature and back contact of relay 10, inner armature and front contact of relay 11, back contact and righthand armature of relay 12, through the winding-of relay 13, arm 14 (position 3), brush 16, terminal 64, conductor 34, outer right-hand armature and front contact of relay 33, arm 35 (position 1) through the winding ofconnector primary magnet 36 to grounded battery; Magnet 36 in response to the intermittent completion of this circuit steps brushes 37, 38 and 39 of the connector switch to the group of terminals containing those of the wanted linef Relay 13 is also energized in the impulse circuit retaining its armature attracted throughout the series of impulses and completing a circuit from ground, front contact 'and armature of res lay 13, arm 19 (position 3), brush 17, terminal 28, arm'40 (position 1), back contact and armature of relay 41. through the winding of connector escape magnet 42 to grounded battery, and in parallel With this circuit from arm 40 through the winding of slow release relay 43 to grounded battery. Escape magnet 42 and relay 43 are energized in these circuits, relay '42 performing no operation at this time, but relay 43 completing a locking circuit for relay 33 which may be traced from grounded battery through the winding of relay 33, inner right-hand armature and frontv contact of said relay, front contact and left-hand armature of relay 43., terminal 29, brush 18, arm 27 (position 3), conductor 30, outer armature and front contact of relay 11 to ground. At the conclusion of this series of impulses, relay 13 deenergizes to interrupt the circuit for relay 43 and escape magnet 42. Escape magnet 42 is deenergized to advance connector side switch arms to their second position. Relay 43 opens the locking circuit traced for relay 33, but this relay'is held energized over a substitute locking circuit which may be traced from grounded battery, through the winding, inner armature andfront contact of relay 33,'conductor 44, arm'32 (position 2)-and thence over the original energizing circuit of relay '33 to ground at the outer armature of relay .1.

The subscriber now operates his Sender 2 to send the units serles of impulses. As

' before relay lOresponds to these impulses,

terminal 64, conductor 34, outer right-hand armature and front contactof relay 33,-arni 35 "(position 2) through the winding of secondary magnet 46 to groundedbattery; Magnet 46 responds-to the intermittentcompletion of this circuit to stepbrushes-37, 38'

and 39 into engagementwiththe'terminals of the called line.

magnet 42 and slow release relay; 43 which are the same as those previously traced. with the exception that arm 40 is now'in position 2. At theend ofthis' series of impulses relay 13 retracts its armature,'interrupting these circuits to deenergize magnet 42 which thereby asses the connector side switch arms to their'third position. "Relay" 43,being slow to release, however, maintains the first" traced locking oircuitf'for relay33 until the called. line is tested.

If the called line is busy," ground poten tial will be present on'its test terminal 47, being supplied thereto from ground over the front contact and'left-hand armature of testrelay 48, arm 49 (position 3), and brush 39 of the connector switchwhich s in engagement with a multiple of terminal 47, or from ground through the right-hand low-resistance winding of the relay 48, arm 49 (position 4) and brush 39 ofsuch a switch, or if the line is busy as a calling line, from the line or first selector switch in the well-known manner. This ground potential present on terminal 47 shunts test relay 48 and there being no longer any circuit for relay 43, this relay after a short interval retracts its armature to open the locking circuit of relay 33. Relay 33, in deenergizing completes a circuit from grounded battery, left-hand armature and back contact of relay 33, th-rough'the winding of release magnet 31 and off-normal con tact 50, closed when the brushes took their first step, to ground.

Relay 13is-also energlzed 1n the circuit Just traced and completes the energizmg clrcuits for escape Magnet 31 is energizedin thiscircuit to restore the brushes, off-normal contact, and slde'switch arms of the connector switch to their normal pos'b tion, but'before contact 50 opens, contact 51 is closed to complete a substitute ;.hold-'- ing circuit for magnet '31, which may 1:12 traced from grounded battery, left hand armature and back contact of-relay' 33', net 31, contactiel, resistance 52, front con-'- tact and left-hand armatureof magnet 31,

terminal 29, brush 18,. arm 27 (positionfi), conductor 30, outer-armature and front contact of relay 11 to ground When the side switch arms reach their normal position arm '54 completes a busy tone circuit from ground through thesecondary winding of busy tone source 53,'front contact andright-v hand armature of magn'et 31, arm 54 (position I), condenser 55, terminal 28, brush 17' arm 19' (position 3),armatureand back con tact 'of relay 13, winding of relay 12, throughv the" lower right-hand winding} of repeating coil 9. to grounded battery. -:This 7 tone is repeated to the calling subscriber by; induction through the lower left-hand wind lllg -Qf repeating coil 9.:and l1e;;replaceshis receiver on its hook." Relay lO-is thereby deenergized to open the .circuitlofrelay '11..

Rela 11. inretracting its inner armature,

completes. 'acircuit from grounded battery:

through the winding er? selector release-mag;

net 56', contact-5 7, closed-i when thefseleotori switchv -left ;1ts=normal:' position, loacktj con-i:

tactiand'inner armatureof relay ll,wback contact and armature-10f relay 10 aground. i

Magnet 56' is energized in", this circuit'xandf releases the -'selector switch. Relay- 1111 retracting its" outer Iarmature- .remo'ves ground potentiall fromterminal 8"thereby' ously traced holding circuit for connector release magnet 31, which magnet thereupon becomes: inert and the neXtcalL. a

If the called line is found idle, battery potential will be present'on its test terminal 47, being supplied. through the windingof its releasing the line switch in-: the, well-known" Tl .manner as-Twell asmterrupting-the previ the system is ready; for

cut-off relay and a circuit will be completed 3 through brush- 39, arm 49 (position 3) lefthand high resistance winding of relay 48 to ground. The cut-off relay of thecalled line and relay 48' are energized in this circuit, re-

lay 48 in attracting itsleft-hand armature V shunting its left-hand winding to supply full ground potential to testterminal 47 as previously described; Relay 48in attracting its rightshan'd armature'completes a locking circuit from: ground through its right-hand low resistance Winding,right-hand; armature and" front contact, arm- 40 (position 3), through the winding ofrelay 43, to grounded battery and in parallel with this circuit throughthe winding of escape magnet 42' to grounded battery. Relay 43fretains its armatures attracted thereby maintaining the 5 lOcking circuit of relay 33.- Magnet 42 in attracting its armatures completes a ringing circuit from a source of ringing current through the winding of marginal trip relay 41, left-hand armature and front contact of magnet 42, arm 65 (position 3), brush 38 and its associated terminal, through the ringer at the called substation, brush 37 and its associated terminal, arm 58 (position 3), front contact and right-hand armature of magnet 42 to ground. The bell of the called line is rung in this circuit, but relay 41 is marginal and will not be energized until the called subscriber answers. A portion of the ringing current is also transmitted from the source of current through the winding of relay 41, left-hand armature and front contact of magnet 42, conductor 59, arm 54 (position 3), condenser 55 to terminal 28' and thence over the path previously traced for the busy tone to the calling subscriber, who is thereby informed that the called line is being signalled. .Nhen the called subscriber removes his receiver from its hook, he lowers the resistance of the ringing circuit to energize relay 41.- Relay 41, inattracting its armature, opens the circuit of escape magnet 42, which is deenergized to (position 3), armatureand back contact of relay 13, through :the winding of relay 12 and the lower right-hand winding of impedance coil 9 to grounded battery. Relay 12 is energized in this circuit and completes an energizing circuit for magnet 21, from ground, left-hand armature and front contact of relay 12, arm 20 (position 3), through the winding of magnet 21 to grounded battery. Magnet 21 in energizing passes the selector side switch arms to their fourth position. In the fourth position of the connector side switch, relay 33 is held energized from grounded battery, through its winding, inner right-hand armature and front contact, conductor '44, arm 32 (position 4), back contact and left-hand armature of magnet 31, terminal 29, brush 18, arm 27 (position 4), conductor 30, outer armature and front contact of relay 11 to ground. In passing from its third to its fourth position, arm 23 removed condenser 22 from its connection across the calling line and connected a noninductive resistance 61 in parallel with impulse relay 10. This resistance 61 offers a better path for voice current. than the winding of relay 10, but is adjusted to allow sufficient current to flow through relay 10 to hold said relay energized and this relay becomes a supervisory relay controlling re) lease of all the switches employed in building up the connection. With the selector and connector side switches in position 4 a talking circuit is completed between the calling and the called lines over the conductors shown in heavy black, talking current being supplied to the calling line from grounded battery through the lower left-hand winding of repeating coil 9, arm 23 (position 4), resistance 61, terminal 7, brush 4, through the calling substation 1, brush 3, terminal 6 and upper left-hand winding of repeating coil 9 to ground, talking current being supplied to the called line from grounded battery through the lower right-hand winding of repeating coil 9, and thence in parallel through f the winding of relay 12 and its non-induc tive shunt 62, back contact and armature of relay 13, arm 19 (position 4), brush 17, terminal 28, arm 65 (position 4), brush 38 and its associated terminal, through the called substation, brush 37 and its associatedtermi-' nal, arm 58 (position 4), terminal 64, brush 16, arm 14 (position 4) ,arm 63 (position 4), through the upper right-hand winding of repeating coil 9 to ground.

At the completion of when the calling subscriber replaces his receiver on its hook, he interrupts the circuit of supervisory relay 10 which, in retracting its armature, opens the circuit of relay 11 r and completes the circuit for release magnet 56 in the manner previously described. Relay 11, in retracting its outer armature opens the holding circuit prev ously traced for rethe conversation,

lay-33, which in deenergizingcloses the pres f viously traced circuit for release magnet 31.

The removal of ground potential from ter minal 8' also releases the line switch and the apparatus is now completely restored.

Thus is appears that by the connection of a condenser in parallel with the supply of talking current, during the time that switches are being set, a series relay may be made responsive to impulses of short duration regardless of the high impedance of the line circuit caused, by the'presence in the line of impedance or repeating coils. When the called subscriber responds to the call, the condenser, which would, of course, destroy the talking qualities of the calling loop, is removed from its position across the line and a non-inductive shunt is connected in parallel with the impulse relay to provide a better pathfor voice current and to enable the impulse relay to be used as a supervisory relay.

WVhat is claimed is:

1. In a telephone system, the combination with a line circuit, an automatic switch, a stepping relay, a non-inductive resistance, and a condenser, 'of means for including said relay and said condenser in said line circuit, an impulse sender in said circuit for operating said relayto set said switch,'-and means for substituting said resistance for said condenser whensald switch is set;

2. .In a telephone system, the combination of a telephone line, a trunk circuit, means for connecting said telephone line to saidtrunk circuit, a stepping relay in said trunk circuit, battery feed coils and a source ofcurrent connected across said trunk, a circuit includinga, condenser in'parallel with said coils and source of current, an impulse's'ender in said telephone line to intermittently operate said stepping relay, a called 'line, means re sponsive to the operation of said relay for extending said trunk circuit to said called line, and means for thereafter interposing a break in the circuit of said condenser.

3. In a telephone system,the combination 7 line, means responsive tothe operation of said relay for extending said trunk circuit to said called line, a non-inductive resistance,

and, means operated after the extension of V saidtrunk line to said called line for inter-2 posing a break in the c1rcu1t cfsa ld conden- ,serand for includingsal d n'onnductivere- Y sistance in shunt of said relay; 1

V 4. In a machine switching-telephone system, the combination o'fa telephone line, an impulse sender associated therewith, atrunk circuit in association with said telephone a source of current connected to said trunk circuit, impedance coils in series with: said source of currentto exclude voice currents I therefrom, a circuit including'a condenser connected across sald trunkrcircuit 111, parallel with sa d source of current and 1mpedance coils to render said s'eries relay re;

-sponsive to the operation of said impulse a a sender, a calledll1ne, means responslve to the operation of said relayirforriextending' said trunk circuit'to Isaid called line, means re sponsiveto such extensionjforgsignaling said called line, and means actuated by theresponse of-the called sub criber for interposing'a break in said condenser circuit.

5. In a; machine switching telephone sys line, a relay in series with said trunk circuit, a repeatin'g coil, a source of current 7 connected to said trunk c1rcu1t through the windings of said repeatlng'coil, a circuit ntem, the combination with, a. telephone line, 1 an impulse sender associated therewith, a trunk circuit associated with said telephone] eluding a condenser connected across said trunk circuit in parallel with said repeating coil to render said series relayv responsive to the operation of said impulse sender, 'a'called line, means responsive to the operation of said relay for extendingsaid trunk circuit to said called line, means responsive to such extension and to the idle condition-ofsaid called line for signaling said called line, and; means actuated by-the response ofthecalled subscriber for opening said condenser cir cuit and closing anon-inductive-pathfor; current in parallelwith said series relay. V t to v j In witness whereof, I hereunto subscribe Q"; 'my name this 17th day of NovemberA; D i V 1919. t line, a relay in series with said trunk circuit,

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